net: Separate out SKB validation logic from transmit path.

dev_hard_start_xmit() does two things, it first validates and
canonicalizes the SKB, then it actually sends it.

Make a set of helper functions for doing the first part.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 71 insertions, 54 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 6d82194e414b..704a5434f77d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2644,80 +2644,97 @@ out:
         return skb;
 }
 
-int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
-                        struct netdev_queue *txq)
+struct sk_buff *validate_xmit_vlan(struct sk_buff *skb, netdev_features_t features)
 {
-        int rc = NETDEV_TX_OK;
+        if (vlan_tx_tag_present(skb) &&
+            !vlan_hw_offload_capable(features, skb->vlan_proto)) {
+                skb = __vlan_put_tag(skb, skb->vlan_proto,
+                                     vlan_tx_tag_get(skb));
+                if (skb)
+                        skb->vlan_tci = 0;
+        }
+        return skb;
+}
 
-        if (likely(!skb->next)) {
-                netdev_features_t features;
+static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device *dev)
+{
+        netdev_features_t features;
 
-                /*
-                 * If device doesn't need skb->dst, release it right now while
-                 * its hot in this cpu cache
-                 */
-                if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
-                        skb_dst_drop(skb);
+        if (skb->next)
+                return skb;
 
-                features = netif_skb_features(skb);
+        /* If device doesn't need skb->dst, release it right now while
+         * its hot in this cpu cache
+         */
+        if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
+                skb_dst_drop(skb);
 
-                if (vlan_tx_tag_present(skb) &&
-                    !vlan_hw_offload_capable(features, skb->vlan_proto)) {
-                        skb = __vlan_put_tag(skb, skb->vlan_proto,
-                                             vlan_tx_tag_get(skb));
-                        if (unlikely(!skb))
-                                goto out;
+        features = netif_skb_features(skb);
+        skb = validate_xmit_vlan(skb, features);
+        if (unlikely(!skb))
+                goto out_null;
 
-                        skb->vlan_tci = 0;
-                }
+        /* If encapsulation offload request, verify we are testing
+         * hardware encapsulation features instead of standard
+         * features for the netdev
+         */
+        if (skb->encapsulation)
+                features &= dev->hw_enc_features;
 
-                /* If encapsulation offload request, verify we are testing
-                 * hardware encapsulation features instead of standard
-                 * features for the netdev
-                 */
-                if (skb->encapsulation)
-                        features &= dev->hw_enc_features;
+        if (netif_needs_gso(skb, features)) {
+                if (unlikely(dev_gso_segment(skb, features)))
+                        goto out_kfree_skb;
+        } else {
+                if (skb_needs_linearize(skb, features) &&
+                    __skb_linearize(skb))
+                        goto out_kfree_skb;
 
-                if (netif_needs_gso(skb, features)) {
-                        if (unlikely(dev_gso_segment(skb, features)))
-                                goto out_kfree_skb;
-                        if (skb->next)
-                                goto gso;
-                } else {
-                        if (skb_needs_linearize(skb, features) &&
-                            __skb_linearize(skb))
+                /* If packet is not checksummed and device does not
+                 * support checksumming for this protocol, complete
+                 * checksumming here.
+                 */
+                if (skb->ip_summed == CHECKSUM_PARTIAL) {
+                        if (skb->encapsulation)
+                                skb_set_inner_transport_header(skb,
+                                                               skb_checksum_start_offset(skb));
+                        else
+                                skb_set_transport_header(skb,
+                                                         skb_checksum_start_offset(skb));
+                        if (!(features & NETIF_F_ALL_CSUM) &&
+                            skb_checksum_help(skb))
                                 goto out_kfree_skb;
-
-                        /* If packet is not checksummed and device does not
-                         * support checksumming for this protocol, complete
-                         * checksumming here.
-                         */
-                        if (skb->ip_summed == CHECKSUM_PARTIAL) {
-                                if (skb->encapsulation)
-                                        skb_set_inner_transport_header(skb,
-                                                skb_checksum_start_offset(skb));
-                                else
-                                        skb_set_transport_header(skb,
-                                                skb_checksum_start_offset(skb));
-                                if (!(features & NETIF_F_ALL_CSUM) &&
-                                     skb_checksum_help(skb))
-                                        goto out_kfree_skb;
-                        }
                 }
+        }
+
+        return skb;
+
+out_kfree_skb:
+        kfree_skb(skb);
+out_null:
+        return NULL;
+}
+
+int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
+                        struct netdev_queue *txq)
+{
+        int rc = NETDEV_TX_OK;
+
+        skb = validate_xmit_skb(skb, dev);
+        if (!skb)
+                return rc;
 
+        if (likely(!skb->next))
                 return xmit_one(skb, dev, txq, false);
-        }
 
-gso:
         skb->next = xmit_list(skb->next, dev, txq, &rc);
         if (likely(skb->next == NULL)) {
                 skb->destructor = DEV_GSO_CB(skb)->destructor;
                 consume_skb(skb);
                 return rc;
         }
-out_kfree_skb:
+
         kfree_skb(skb);
-out:
+
         return rc;
 }
 EXPORT_SYMBOL_GPL(dev_hard_start_xmit);